Shortly after the discovery of microRNAs in plants, their putative target genes were predicted. Although most of the predicted miRNA targets have no known function, some have crucial roles in cell fate determination hinting to the significance of small endogenous RNAs during plant development. I will use a multi-angled approach to assign developmental functions to miRNA target genes with previously unknown or only putative functions (aim1). I will also make use of a reporter system to determine the normal expression pattern of miRNA-targeted mRNA and protein in planta and compare this to the target mRNA/protein expression pattern that results from disrupting miRNA regulation (aim 2). Finally I will determine the nucleotide positions within target miRNA binding sites that are crucial for maintaining proper miRNA regulation (aim 3). By examining miRNA-mediated gene regulation from different perspectives, I hope to establish the function of miRNA targets, to understand the roles that miRNAs play during the regulation of plant development, and to provide insight into the mechanism of miRNA regulation.